Abstract Melamine and cyanuric acid are environmental chemicals that are found in common household products and can cause kidney injury and damage. Widespread high dose contamination of infant formula with melamine and cyanuric acid led to significant illness and deaths among infants in China due to kidney toxicity, but few studies have examined if lower level chronic exposures may affect kidney health in children. This will be the first study to investigate background melamine and cyanuric exposures in US children and the first to determine their relationship with kidney injury markers. We will measure melamine and cyanuric acid in 800 urine samples from 600 children (600 samples at ages 4-6y and 200 samples at follow-up, ages 8-9y) in the PATHWAYS GAPPS (PWG) cohort, an active cohort funded through the NIH Environmental Influences on Child Outcomes (4UH3OD023271-03) mechanism. We will determine sources of exposure and conduct cross-sectional and longitudinal investigations of urinary melamine and cyanuric acid with urinary markers of renal injury and function: NGAL, NAG, KIM1, proteinuria, and microalbuminuria. The knowledge gained could lead to identification of a novel contributor to kidney injury and disease development. Study results could also be used to reduce exposures in the general population.